1. Field of the Invention
The present invention relates to a method of and an apparatus for evaluating various quality items, e.g., the shape, flaws, voids, etc., of an elastic member.
2. Description of the Related Art
A solid polymer electrolyte fuel cell employs, for example, a membrane electrode assembly, which comprises an anode electrode, a cathode electrode and an electrolyte membrane interposed between the anode electrode and the cathode electrode. The electrolyte membrane is comprised of a polymer ion exchange membrane. The membrane electrode assembly and separators sandwiching the membrane electrode assembly make up the fuel cell. Each of the anode electrode and the cathode electrode comprises a base made chiefly of carbon and an electrode catalyst layer of precious metal joined to the base.
Each of the separators is comprised of a carbon-based material and sheet metal, and includes a resin seal member (elastic member) for preventing reactive gases and a coolant from leaking out. If the resin seal member has flaws and voids (air bubbles), then it fails to keep a desired sealing capability when the fuel cell is placed under a predetermined tightening load.
Therefore, it is necessary to evaluate the quality of resin seal members for rejecting defective resin seal members. One known quality evaluating apparatus is disclosed as an appearance inspecting apparatus in Japanese Laid-Open Patent Publication No. 2003-166949, for example. The disclosed appearance inspecting apparatus comprises an image capturing unit movable in X and Y directions over the surface of a printed-circuit board or the like that is fixedly placed in a test position, an X-direction illuminating unit mounted on the image capturing unit for illuminating a given area in the X direction, and a Y-direction illuminating unit mounted on the image capturing unit for illuminating a given area in the Y direction. The image capturing unit is stopped at a predetermined position over the surface of the printed-circuit board, and the X-direction illuminating unit and the Y-direction illuminating unit are alternately energized.
When a flaw or defect extending in the Y direction is imaged by the image capturing means, it may not easily be visually confirmed if it is illuminated by only the X-direction illuminating unit. However, the image of the flaw or defect can clearly be seen if it is illuminated by the Y-direction illuminating unit. Conversely, though a flaw or defect extending in the X direction may not easily be visually confirmed if it is illuminated by only the Y-direction illuminating unit, it can clearly be seen if it is illuminated by the X-direction illuminating unit.
According to the conventional appearance inspecting apparatus, however, since the X-direction illuminating unit and the Y-direction illuminating unit are alternately energized and the illuminated flaw or defect is imaged by the image capturing unit, the entire appearance inspecting process is tedious and time-consuming. Though the conventional appearance inspecting apparatus is able to inspect the surface of a printed-circuit board or the like for flaws and defects, it is incapable of detecting voids inside an elastic member, for example. Accordingly, it has heretofore been difficult to detect the quality of elastic members highly accurately.